Press-in elements are known, for example from document EP 0678679 B1. There an element which can be inserted into a sheet metal part is claimed which consists of a shaft part and a head part formed in one piece thereon, with the element having concave peripherally closed fields at its underside which serves as a contact surface and also at least one recess extending spirally around the shaft part. The spiral recess is preferably formed by a thread groove consequently also bounded by a thread turn which can be regarded as a ring bead. The elements can be realized as a nut element or as a bolt element. The element described there has proved itself in practice but is however not necessarily suited for usually very thick sheet metal parts (for example with a thickness of 4 mm or larger).
A modified variant of the elements is furthermore known from EP 0958100 B1 and indeed there in the form of a bolt element which can be introduced in self-piercing manner into a sheet metal part, but which can also be introduced into a pre-pierced metal sheet. The element is in particular suitable for being used in relatively thin metal sheets, i.e. of up to approximately 2 mm thickness. The design of the element in the region of the head part corresponds largely to the design of the element in accordance with the above-named document EP 0678679 B1.
Furthermore, reference should be made at this point to WO 94/01688 which describes a press-in part as a fastener element in the form of a bolt, a screw or an internal thread carrier acting as a type of nut and indeed in order to obtain a joint to a sheet metal part which is resistant to press-out and rotation. In this connection the element has head part of larger diameter having a contact surface substantially radial to the longitudinal axis, a shaft part of smaller diameter extending at one side in the axial direction beyond the contact surface and, in the transition region between the head part and the shaft part, a radially outwardly open restriction concentric to the longitudinal axis as a ring space for the accommodation of the sheet metal material. The radially outwardly open restriction is formed by a ring projection which extends in the radial direction and surrounds the shaft part.
In all the above explained known elements the sheet metal material is moved radially into a ring recess or a thread turn formed by the ring projection or a thread turn by a die button arranged below the sheet metal part which has a special form in order to bring about this material flow, i.e. into the radially open ring recess and optionally into the concave fields. This manner of proceeding is entirely practicable for sheet metal parts up to about 2.5 or 3 mm. However, when the sheet metal part becomes significantly thicker it is not possible or hardly any longer possible to introduce sheet metal material into the corresponding ring recess by the action of a die button.